Onion Epidermis Under the Microscope
Onion Epidermis (Whole Mount), Allium cepa
This is a thin layer of onion skin (epidermis) mounted flat and stained with fast green. It is one of the most common first slides in biology because its large, simple plant cells are easy to see.
This is a whole mount of onion epidermis (Allium cepa), a thin skin peeled from an onion bulb layer and stained with fast green. It is only one cell thick, and the cells are long, narrow rectangles lined up in rows like bricks in a wall. Each is outlined by a cell wall, a stiff layer made of cellulose that gives plant cells their boxy shape. A large central vacuole fills most of each cell, and small dark nuclei can be spotted in some of them. This is a classic first slide for comparing plant cells with animal cells.
Labeled onion epidermis under the microscope
- Cell wall: Stiff outline that gives each cell its boxy shape
- Nucleus: Round body, often pressed against the wall
- Vacuole: Large central space that fills most of the cell
What to look for
- Cell wall: Clear green outlines around each long, rectangular cell.
- Nucleus: A small round or oval body, often pressed near the side of the cell.
- Vacuole: A large central space that fills most of each cell and pushes the cytoplasm to the edges.
- Cytoplasm: A thin layer lining the inside of the cell wall.
Questions and answers
What do onion cells look like under a microscope?
Onion epidermis cells are long rectangles packed together like bricks. Each cell has a clear cell wall, a nucleus often near one side, and a large vacuole that fills most of the cell.
Why don't onion cells have chloroplasts?
The onion layers used for this slide are part of the bulb, which grows underground where there is no light. Without light for photosynthesis, these cells do not need chloroplasts.
How are onion cells different from cheek cells?
Onion cells are plant cells, so they have a rigid cell wall, a boxy shape, and a large vacuole. Cheek cells are animal cells, with no cell wall and a more irregular, flat shape.
Compare it
- Category
- Botany & Plants
- Scan magnification
- 20x
- Stain
- Fast Green
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